Self-stripping perforation punch



March l5, 1955 Filed P. H. TAYLOR SELF-STRIPPING PERFORATION PUNCH Nov. 23, 1951 2 Sheets-Sheet 1 March l5, 1955 P. H. TAYLOR 2,704,125

SELF-STRIPPING PERFORATION PUNCH Filed NOV. 25, 1951 2 Sheets-Sheet 2 VEN TOR.

2,704,125 n SELF-STRIPPING PERroRATloN PUNCH Paul H. rlaylor, Grand Island, N. Y., assignor to Wales- Strippit Corporation, North Tonawanda, N. Y., a corporation of New York p i appiicann November 23, 1951, serial No. 257,792

12 claims. (ci. 164-110) This invention relates to an instrumentality for perforating metal sheets, plates, bars, structural elements and the like; and more particularly the in vention is concerned with an instrumentality for the purpose described characterized by a resilient means which is compressed incident to the performing-stroke of the punch and which is permitted to expand upon completion of such stroke to strip the work-piece from the punch.

' The invention is characterized by features which adapt it particularly for use in connection with portable perforating instrumentalities of the self-contained, or unit, type. The punch and die elements of such instrumentalities are ordinarily supported in cooperating relation with respect to one another by the upper and lower arms of a holder, and in most instances have the objection that the loading of the spring employed to strip the workpiece from the-punch after the perforating operation is accomplished by compressing the spring between the head of the punch and the upper arm of the holder. Consequently, the upper arm of the holder is subjected to excessive down loads at the same time that the punch is being driventoward and through the workpiece. Such down loads upon the upper arm of the holder cause deflection of the arm, and as such arm carries the punch, shifting of the punch toward one side of the die and away from the other results, thereby producing a hole of unlike configuration on opposite sides. There is no serious objection to the stripping load being applied to theupper arm ofthe holder when the punch is being withdrawn from the Work-piece as deflection of the upper arm during such time has no effect on the configuration of the hole previously produced by the punch.

The Wales Patent 1,955,866 discloses a self-contained perforating instrumentality in which the punch is surrounded by a stripping collar, there being a spring interposed between the stripping collar and the head of 'the punch in such a manner as to avoid the application of down loads to theupper arm of the holder incident to the loading of the stripping spring, the forces released when the latter is permitted to expand acting directly against the work-piece Arather than against the upper arm of the holder.

The perforating instrumentality of the present invention, as is true of the instrumentality disclosed in Wales Patent 1,955,866, avoids any down loads upon the upper arm of the holder incident to the loading of the resilient means employed in stripping the work-piece from the punch. While in the present invention the stripping load is transferred to the upper arm of the holder in withdrawing the punch from the Work-piece, this occurs after the perforating operation has been completed and in no way adversely affects the configuration of the hole.

The perforating instrumentality of the invention avoids the use of mechanical springs for stripping the punch from the work-piece and contemplates for this purpose the use of a compressible iluid in the manner disclosed and claimed in my copending application Serial No.

185,604, tiled September 19, 1950.

One obiect of the invention is to provide a simplitied form of punch and in so doing enable the provision of a simplified punch and die assembly.

A still further object is to provide an assembly of the character described wherein the cooperating punch and die elements are so formed as to minimize the force nited States Patent@ required forA stripping the punch from the work-piece 2,704,125 Patented Mar. 15, 1955 ICC erations are developed without loading the arm of the holder which carries the punch.

A still further object is to provide a perforating assembly wherein the parts cooperate in such a manner as to insure the formation of accurately shaped holes.

A still further object is to provide a punch which carries the means by which the stripping forces are developed and released.

Av still further object is a novel design and arrangement ofthe parts of the instrumentality, whereby to provide for economy in construction, facilitate assembling and dis-assembling of the parts and insure accuracy and dependability in operation.

The invention is illustrated in the accompanying drawings, wherein:

Figure l is a side view, partially in elevation and partially in section, of a perforating instrumentality e'mploying the features of the invention;

Figure 2 is a fragmentary sectional view showing the positions of the parts at the limit of the perforating stroke of the punch; and

Figure 3 is a fragmentary section showing the manner in which the punch is stripped from the work-piece upon completion of the perforating operation.

The perfor-ating instrumentality illustrated, indicated generally at 2i), is in the form of a self-contained, or unit, assembly, and is shown supported upon the bed 21 of a, press, the ram of the press being indicated at 22 in an elevated position;

The perforating instrumentality 20 includes a holder 23 for mounting punch and die elements 24 and 2S, respectively, in aligned operation relation, the punch 24 occupying a guide bore 26 in the upper arm of the holder and the die 25 being carried by the lower arm. The punch 24 is normally heldin an elevated position by a lifter spring 27 having one end fixed to the upper arm of the holder and the free end occupying a notch 2S in the upper end of the punch. The-lifter spring 27 serves only to hold the punch in the elevated position shown in Figure l and to return it to such position upon completion of the perforating operation.- yIt may, therefore, be of light construction, as illustrated; and its loading incident to the operation of the punch does not result in the transfer to the upper arm of the holder of any loads capable of deecting said arm.

rfhe punch 24, as illustrated, is hollow and forms a chamber 29 for a body of a compressible uid 30 which is preferably a liquid such as mineral oil, a silicone oil, or the like. 'The lower end of the punch 24 is of reduced diameter and is formed with a threaded entrance 31 leading to the chamber 29 and accommodating a threaded flange 33 of a cylinder 34. The latter extends into the chamber 29 and a wall portion 35 thereof is spaced from the walls of the chamber, it being noted that the anged end of the cylinder 34 is inset with respect to the lower end of the punch to provide a cavity. v

The cylinder 34 accommodates a plunger 36 which carries a head 37 at its lower end and which at its upper end is formed withan annular channel 38 for accommodating a sealing ring 39. At opposite sides of the channel 38, the plunger 36 may be chromium plated as indicated at 4t) to provide surfaces highly resistant to any grrosive action of the fluid medium in the chamber As illustrated at Figure 1, the body of fluid in the chamber 29 completely tills the chamber and the inner end of the cylinder 34 when the plunger 36 occupies the extended position shown in which the head 37 is located in advance ofl the lower end of the punch, the said fluid preferably being uncompressed at such time.

It will be apparent, therefore, from the foregoing that when the punch is actuated to perforate' the work-piece,

indicated -at 41, -the rhead 3.7 `of the plunger will engage.v

the work-piece so that the plunger will be held stationary during the-initial part of the movement of the punch toward the 'work-piece. During this portion fofthe @travel of the punch, therefore, the uid medium in the chamber .29 -w'ill be compressed .bythe plunger.

Tzhe fhead 37 of the plunger moves into the .cavity -in the end of the punch as the flatter .engages the work-piece and is moved to the position shown in Figure 2 ftd-perforat'e the Work-piece tand lodge in 'the die 25 the slug 42 vthus produced. .At this time, lthe plunger 36 is urged 4ag'ainstgthe slug 42 by the compressed -fluid in the chamber 29 but the slug 42 engages Ythe Walls -of the die aperture tightly and ythe .pressure exerted by the plunger is insutlcient to ydrive the :slug :through the die aperture.

Upon completion :of `the perforating operation, the :ram 22 :of the press is elevated, iat :which -time .the compressed :udinftlt'e chamber 29 expands to extend the plunger 36 in the manner illustrated in Figure 3. As this occurs,

-the punch .24 .is elevated carrying ythe work-piece 41 with .it until the work-piece `engages the upper .arm of Vthe holder. Further movement of the work-piece being prevented while upward movement of the punch is continued, the punch is stripped from thework-piece and is then .car- -ried to its normal elevated .position by .the lifter spring l27. A succeeding stroke of the punch 24 causes 'anotherxslug to enter the `die aperture, :driving vthe :rst slug into the reliefportion 44 of the vdie so that it irnay fall by gravity into the slug clearance chute 4S.

The lower end of the punch 24 vis preferably conically shaped as vat 43, the diameter ofthe cutting edge at the extremity of the punch being 'such that such extremity may enter the die aperture with suicient clearance to prevent jamming. In this case, the upper, or major, diameter of the conical section 43.is preferably made greater than the diameter ofthedie aperture and greater than the diameter of the cutting extremity by .at `least per cent of the height of such section. It will be noted in this connection that in the use of the vinstrumentality the punch 24 enters the die aperture just sufficiently .to'completely sever :the slug from the work-.piece and so that the conical .section 43 of the punch will occupy the 'aperture produced in the work-piece. The construction described 'has the advantage that the force yrequired to strip 'the work-piece from the punch is reduced and the range over 'which such force is required is also reduced. The use of 'a'tapered punch -is thus particularly desirable when a uidmedium .is employed to develop and release stripping forces 'in the 4manner described as such forces, although large, are most 'effective 'over a short range. 4It will be understood, however, that the invention is not limited to 'the llow-pressure range of 'the compression 'strokes of the `plunger 36 andis'ealing during the high pressure range 'of such strokes maybe obtained by so designing the cylinder 34 that it will be compressed around the plunger as disclosed and claimed in my `copending application Serial No. 180,966, tiled August 29, 1950.

It will be apparent that the instrumentality described enables the vattainment of the objects set out and avoids the'necessity for the luse 4'of stripping collars, mechanical springs (for stripping purposes), or the necessity 'for the use of special and additional parts in connection with the punch to enable stripping of the work-'piece from the punch. The linstrumentality described, therefore, is simple and economical in design and is highly accurate'in operation.

paratus.

I claim as my invention:

l. Ina punching apparatus, a reciprocable punch 'having 'a chamber therein, a Ibody of compressible liquid .filling said chamber, a work-engaging member reciprocable vin said chamber'an'dconstantly'urged'toward'engagement with 'thefworkby 'saidi body ofli'quid andp'ositioned to'engage the work to compress said body of liquid during a .working .stroke `of the punch .so `that .upon .completion .of

said working stroke said body of liquid expands to return said punch toward original, inoperative position, and means fixed relative to said punch position between the extremities of movement of the front operating face of said punch, to engage and strip the work from the punch on the return stroke of the punch.

2. In apparatusfor perforating a workpiece, a reciprocable punch having a chamber therein, a body of compressible liquid flling `said chamber, 'a plunger reciprocable in said chamber andoperable against said .body of liquid and having a portion normally protruding beyond the front .operating faceof .said punch, said body of liquid constantly urging vvsaid plunger outwardly 'beyond said front operating face, :saidplunger being positioned to engage the work-piece during a working stroke of the punch to compress said body of liquid so that upon completion ,of .saidfstroke :said/body .of liquid expands to return said punch 'toward original, inoperative position, and `.means xed .relative .to said :punch zand positioned vbetween .the extremities of movement ofthe .front 4.operating face Aof -said .punch, to engage and strip the work from 'the punch .on the -return stroke of .thejpunch.

`hAn assembly includinga pimch and a die .between which a work-piece may zbe introduced -so -that .the latter may beperforated,fsaid punch in itsworking stroke .being adapted to :enter the die just sufficiently vto completely sever .a slug from the work-,piece :and to lodge the slug .in .said die, and apunch-returning member carried by said punch, resilient .means connecting said punch-returning member to 4said punch and constantly urging said punch- `returning member outwardly beyond that face of said punch which Afaces :the die, said punch-returning member .acting against said slug tostore energy vin said resilient `means during the .punching stroke for .returning said punch, and means .stationary relative to said punch and positioned between the yupper and .lower extremities of `movement-of that :face `of .-said punch which faces said die fto strip the work-'piece ifrom said .punch on return movement ofsaid punch.

4. .Apparatus fforperforating a work-piece comprising a frame, apunch reciprocable in said frame, a cooperatring die carried by Vsaid frame, said punch being movable toward said die under -force during a working stroke to perforate a work-piece, that has been introduced between the .punch and die, and yto lodge the slugproduced in said die, .a punch-'returning member, :resilient means interposed 'between said punch-returning-member and said punch for constantly urging the punch-returning member outwardly beyond the operating end face of said punch, said punchreturning member 'being disposed to engage, during the working stroke 4of thepun'ch, the portion of the workpiece, ffrom which the slug "is produced, to compress said resilient means, whereby `when the force on said punch is released, vvsaid resilient means will expand 'to return said punch, and fmeans fixed relative to said frame and posi- Etioned `between the extremities of movement of the op- 'erating end lface ofthe punch to strip the work-piece from saidpunch.

5. An assembly including a reciprocable punch and a die between 'which =a work-piece may be introduced so `that thework-piecelmay `be perforated, the working stroke Iof said `punch being just 'sufficient for the punch to sever -a'slugtfrom the work-piece and lodge the slug in said die,

' saidpun'ch having :a chamber therein filled with a body of compressible liquid, punch-returning means carried by lsaidipunch and normally :protruding beyond the operating :front face sof said punch to engage the portion 'ofthework=piece,'from which'theslug'is produced, before Athe punch engages the `work-piece, said .punch-returning fmeans Ibeing disposed to compress said body of liquid during the :perforating operation, whereby upon release 'of the :perforatng -force, .said body of liquid will expand 'to return said punch, 'and means `stationary `relative to said punch and-disposed lbetween the extremities of movement of the operating front iace-of'said punch, to strip the work-piece :from said punch.

f6. .An assembly. including a Vreciprocable punch .and a die between which a work-piece may be introduced so thatthe work-piecemay be perforated, the working stroke of saidpunch being just sufcient for the punch to sever `a Aslug from the Work-piece 'and lodge kthe slug in said die, `said punch having a chambertherein tilled with a 'body of punch and normally protruding beyond the operating front face of said punch to engage the portion of the work-piece, from which the slug is produced, before the punch engages' the work-piece, said plunger being operatively connected to said body of liquid to compress said body of liquid during the perforating operation, whereby upon completion of the working stroke of the punch, said body of liquid will expand to return said punch, and means stationary relative to said punch and disposed between the extremities of movement of the operating front face of said punch, to strip the work-piece from said punch.

7. An assembly including a frame, cooperating punch and die elements carried by said frame between which a work-piece may be introduced, said punch element being movable toward said die element during a working stroke to perforate said work-piece and lodge the slug produced in said die element, work engaging means carried by said punch element, and compressible means interposed between said punch element and said work-engaging means and constantly urging said work-engaging means outwardly beyond the front operating face of said punch element to engage the portion of the work-piece from which the slug is produced, and acting through said work-engaging means against said slug during the working stroke of said punch element to store energy for returning said punch element, upon completion of its working stroke, to its original position and stationary means iixed relative to said punch element and positioned between the extremities of movement of the operating front face of said punch element to engage and strip said work-piece from said punch element on return movement of said punch element.

8. An assembly of the character described comprising a frame having upper and lower arms, a punch carried byY said upper arm and reciprocable therein, a cooperating die carried by said lower arm, said arms supporting said punch and die in spaced relation to enable a work-piece to be introduced between them, said punch being movable toward said die during a working stroke to perforate s'aid work-piece and lodge the slug produced in said die, a punch-returning member carried by said punch and positioned to engage the portion of said work-piece, from which said slug is produced, on the working stroke of said punch, resilient means interposed between said punch and said member and constantly urging said member to project forward of the operating front face of said punch to engage the work-piece, on the working stroke of said punch, before the punch engages the work-piece, whereby said resilient means will be compressed during the perforating operation and will expand upon completion of the working stroke of said punch to cause said member to return said punch, and said upper arm having its lower face positioned between the extremities of the movement of the operating front face of said punch to engage the workpiece on the return movement of the punch to strip the work-piece from said punch.

9. An assembly of the character described comprising a frame having upper and lower arms, a punch carried by said upper arm and reciprocable therein, a cooperating die carried by said lower arm, said arms supporting said punch and die in spaced relation to enable a work-piece to be introduced between them, said punch being movable toward said die during a working stroke to perforate said work-piece and lodge the slug produced in said die, said punch having a chamber therein, a body of compressible liquid in said chamber, a punch-returning member carried by said punch and positioned to engage the portion of said work-piece, from which said slug is produced, on the working stroke of said punch, before the punch engages said work-piece to compress said body of liquid during the perforating operation, said body of liquid expanding upon completion of the working stroke to cause said member to act against said slug to initiate the return of said punch to its original position, and means iixed relative to said punch and disposed between the extremities of movement of the operating front face of said punch to en gage the work-piece on the return movement of said punch to strip the work-piece from said punch.

10. Apparatus for perforating a work-piece, comprising a cooperating punch and die between which a work-piece 6 may be introduced, said punch being movable toward said die during a working stroke to perforate said work-piece and lodge the slug produced in said die, a plunger reciprocable in said punch, compressible means interposed between said plunger and said punch and constantly urging said plunger to project beyond the front operating face of said punch to engage the portion of said work-piece from which said slug is produced during the working stroke of said punch before said punch engages said work-piece, whereby said compressible means is compressed on the perforating operation and said plunger acts against said slug upon completion of said working stroke to initiate return movement of said punch, and means fixed relative to said punch and positioned between the extremities of movement of the front operating face of said punch, to engage said work-piece on said return movement to strip said work-piece from said punch. f

11. Apparatus for perforating a work-piece comprising a frame, a punch reciprocable in said frame, a cooperating die carried by said frame, said punch being movable in the frame toward said die during a working stroke to perforate a work-piece, that has been introduced between the punch and die, and to lodge the slug produced in said die, said punch having a chamber therein, a plunger reciprocable in said chamber, a body of compressible liquid filling said chamber and constantly urging said plunger to project beyond the front, operating face of said punch to engage the portion of said work-piece from which the slug is produced during the working stroke of said punch before said punch engages said work-piece, whereby said compressible liquid is compressed during the perforating operation and said plunger acts against said slug upon completion of said working stroke to initiate return movement of said punch, and stationary means' iixed relative to said punch and positioned between the extremities of movement of the front operating face of said punch, to engage said work-piece on said return movement to strip said work-piece from said punch.

12. Apparatus for perforating a work-piece comprising a frame, a punch reciprocable in said frame, a cooperating die carried by said frame, said punch being movable toward said die during a working stroke to perforate a work-piece, that has been introduced between the punch and die, and to lodge the slug produced in said die, said punch having a chamber formed thereon, a cylinder secured in said punch to project into said chamber, said cylinder opening at its inner end into said chamber and having its outside wall spaced from the inside wall of said chamber, a plunger reciprocable in said cylinder, a body of compressible liquid iilling said chamber and the open end of said cylinder and constantly urging said plunger to project beyond the operating, front face of said punch to engage the portion of the work-piece from which said slug is produced during the working stroke of said punch before said punch engages said work-piece, whereby said compressible liquid is compressed on the perforating operation and said plunger acts against said slug upon completion of said working stroke to initiate return movement of said punch, said frame being fixed relative to said punch and positioned to engage said workpiece on said return movement to strip said work-piece from said punch, and the front face of said punch being recessed to receive the outer end of said plunger when the punch engages the work-piece on the working stroke of tllie punch and during the remainder of said working stro e.

References Cited in the iile of this patent UNITED STATES PATENTS 612,955 Morris Oct. 25, 1898 1,940,438 Stowell Dec. 19, 1933 2,251,135 Iknayan et al July 29, 1941 2,265,331 Wales Dec. 9, 1941 2,346,667 Dowty Apr. 18, 1944 FOREIGN PATENTS 900,511 France Oct. 9, 1944 105,053 Great Britain Mar. 21, 1917 

